This invention relates to a combined clutch/brake apparatus and, more particularly, to a clutch/brake apparatus for use in a machine press or the like.
Combined clutch/brake apparatus are commonly used to drive or brake machinery such as machine presses. Such apparatus usually include a driving member, such as a flywheel, which is rotated by a prime mover such as an electric motor, a driven shaft of relatively low rotational inertia which drives the press reciprocally, a stationary member, normally disengaged clutch plates for connecting and disconnecting the driving member and the driven shaft, normally engaged brake plates for connecting and disconnecting the stationary member and the driven shaft, and an actuating apparatus, which may consist of an operator assembly and a piston actuator, for alternatively engaging and disengaging the clutch plates and the brake plates. To cycle the press, the actuating apparatus is triggered to cause the brake to disengage and the clutch to engage thereby disconnecting the driven shaft from the stationary member and connecting it to the driving member. Deactuating the actuating apparatus terminates cycling because the actuating apparatus causes the brake plates to engage and the clutch plate to disengage thereby connecting the driven shaft to the stationary member and disconnecting it from the driving member.
Starting and stopping the machine cycle may occur frequently, for example, during set-up or when the machine is being cycled through only one stroke at a time. Such frequent starting and stopping causes wear to the clutch/brake apparatus and especially to the clutch and brake plates. Also, every time the clutch is engaged, rotational energy is transferred from the driving member to the driven shaft thereby causing the driving member to decelerate, or slow down. The drive train must bring the driving member back up to speed after each time it slows down to keep its stored rotational energy as constant as possible. As a result, energy is expended each start/stop cycle of the drive train.
One way of minimizing the energy consumption and wear caused by starting and stopping the machine cycle is to arrange the clutch/brake components so as to maximize the effective mass of the driving member and to minimize the effective mass of the driven shaft. Maximizing the effective mass of the driving member maximizes its effective rotational inertia so that its momentum is maximized. Minimizing the effective mass of the driven shaft minimizes its effective rotational inertia so that the amount of energy which is required to accelerate and decelerate the driven shaft is minimized. Consequently, since less energy must be respectively transmitted and dissipated by the clutch and brake plates upon acceleration and deceleration of the driven shaft, clutch and brake plate wear is reduced. Also, since the momentum of the driving member is maximized and the rotational inertia of the driven shaft is minimized, slow-down of the driving member upon clutch engagement is minimized so that the energy that must be replenished by the prime mover is minimized.
However, known clutch/brake units do not include such arrangements. They either add to the effective rotational inertia of the driven shaft, as in U.S. Pat. No. 3,835,971 issued Sept. 17, 1974 to Spanke, et al., or lack arrangements which maximize the rotational inertia of the driving member as in U.S. Pat. No. 3,638,773 issued Feb. 1, 1972 to Lewis, et al. Therefore, it is desirable to provide a clutch/brake apparatus which minimizes the rotational inertia of the driven shaft and maximizes the rotational inertia of the driving member.